Children with moderate to severe bilateral CP have poor upper extremity abilities and segmental trunk control deficits. Their independent functional sitting is impaired with decreased participation in leisure activities, education involvement. Therefore, promoting independent sitting and improving postural and upper extremity abilities are critical to the health and functional independence of children with moderate-to-severe bilateral CP (GMFCS III-IV). Despite significant strides in upper extremity treatments of children with milder (unilateral) CP, there is limited evidence supporting efficacy of treatments targeting seated postural control in bilateral CP. Recent robotic equipment allows clinicians to address engagement, repetition, and intensity to practice task-oriented movements in CP. In this vein, we postulate that robotics can offer a unique platform to provide efficient motor learning-based training in children with bilateral CP by implementing postural skill progression. Our team has developed a unique motorized Trunk- Support-Trainer (TruST) to engage children in play-oriented practice with skill progression. TruST creates a customized donut-like force field at the region of the torso where balance is lost to provide active assistance beyond the sitting stability limits through a belt. The training is based on principles of motor learning, including skill progression. The overall goal of this work is to develop an evidence-based strategy to promote functional independent sitting, maximize seated postural and upper extremity abilities, and improve sitting- related ADLs. Our central hypothesis is that sitting and reaching benefits can be achieved when a motor learning-based postural intervention is combined with postural-skill progression delivered via TruST in comparison to a static trunk support. The innovation of this proposal, (RFA-HD-20- 005, ?Pediatric Rehabilitation?) lies in the fusion of evidence-based clinical practice and novel robotics with TruST. The result is a training paradigm where children with bilateral CP can receive motor learning-based postural training in addition to postural skill progression that is tailored to the child?s postural stability in sitting. If our hypotheses are supported, the TruST-intervention will be a unique therapeutic solution for children with CP GMFCS III-IV to acquire and improve independent functional sitting.